A decrease in mental function often occurs in patients with HIV. Antiretroviral (ARV) drugs are used to treat this but are not entirely effective. Some other therapy could play a role. The drug selegiline in its pill form is used to treat Parkinson's disease, a serious brain disorder. It is believed this drug might protect the brain and repair some damage. This study will use this drug in a "patch" form, which has not been approved by the Food and Drug Administration (FDA), to see if it helps with decreased mental function in patients with HIV. The purpose of this study is to evaluate the use of selegiline transdermal system (STS) in the treatment of decreased mental function in patients with HIV.